local io            = require("io")
local os            = require("os")
local event         = require("event")
local component     = require("component")
local serialization = require("serialization")

local dataCard      = component.data
local cardReader    = component.os_magreader
local cardWriter    = component.os_cardwriter


KEY_FILENAME = 'aes_key'

GREEN_LED    = 4
YELLOW_LED   = 2
RED_LED      = 1


local function generate_key()
    local key = dataCard.random(128 / 8)
    local iv = dataCard.random(128 / 8)

    local key64 = dataCard.encode64(key)
    local iv64 = dataCard.encode64(iv)

    local file = io.open(KEY_FILENAME, 'w')
    if not file then
        print('Could not open file for writing')
        os.exit(3)
    end

    file:write(key64, '\n')
    file:write(iv64, '\n')
end

---Load the key from file
---@return string key
---@return string iv
local function load_key()
    local file = io.open(KEY_FILENAME, 'r')
    if not file then
        print('Missing key file!')
        os.exit(4)
    end
    local key64 = file:read('*l')
    local iv64 = file:read('*l')

    if not key64 or not iv64 then
        print('Invalid key file!')
        os.exit(5)
    end

    file:close()

    local key = dataCard.decode64(key64)
    local iv = dataCard.decode64(iv64)

    return key, iv
end

local function read_card()
    cardReader.swipeIndicator(false) -- control led indicators manually
    cardReader.setLightState(YELLOW_LED)

    print('Swipe the card on the reader...')

    local _, _, _, cardData, cardUniqueId, isCardLocked, _ = event.pull('magData')
    cardReader.setLightState(GREEN_LED)

    print('Data:  ', cardData)
    print('CUID:  ', cardUniqueId)
    print('Locked:', isCardLocked)

    os.sleep(1)

    cardReader.setLightState(0) -- turn light indicators off

    print('Decrypt? [y/N]')
    local ch = io.read()

    if ch ~= 'y' then
        return -- exit
    end

    local key, iv = load_key()

    -- process the data
    local enc = dataCard.decode64(cardData)
    local dec = dataCard.decrypt(enc, key, iv)
    local data = serialization.unserialize(dec)

    print('Owner:', data.owner)
    print('Access:', table.concat(data.access, ','))
end

local function write_card()
    local claims = {
        owner = 'player',
        access = {
            'entry', 'lab'
        }
    }

    local key, iv = load_key()

    -- process the data
    local data = serialization.serialize(claims, false)
    local enc = dataCard.encrypt(data, key, iv)
    local enc64 = dataCard.encode64(enc)
    print(string.len(enc64))

    -- Prompt for the card's display name
    print('Enter card name:')
    local displayName = io.read()

    print('Insert the card into the writer...')

    -- wait for the user to insert the card
    _, _ = event.pull('cardInsert')

    cardWriter.write(enc64, displayName)
end

local subcommand = ...
if not subcommand then
    print('Usage: card_writer <genkey|read|write>')
    os.exit(1)
end
if subcommand == 'genkey' then
    generate_key()
elseif subcommand == 'read' then
    read_card()
elseif subcommand == 'write' then
    write_card()
else
    print('Unknown action: ' .. subcommand)
    os.exit(2)
end